This may be appropos of nothing, BUT when i place my blackberry cradle too close to my computer monitor at work and the email send/receive engages it does cause my screen to jump and there is static on the screen. But only at a range of about 5 inches or less.
Frankly I think this whole issue is seriously overblown. I can assure you that many, many pax leave wireless devices on in flight, either out of ignorance or obstinance and there has never ever been a single incident of a flight being interfered with, much less placed in jeopardy by same.
I believe this is an issue of erring on the side of safety beyond reason and logic.